FIG. 14 shows a conventional brushless DC motor, which is disclosed in Japanese Patent Unexamined Publication No. 2003-284307. The motor contains rectifier 101 for rectifying voltage VAC of AC power supply; DC-DC converter 110 for converting rectified DC voltage (√2)·VAC into low DC voltage VM; smoothing capacitors 109, 111; motor stator-coils 103, 104; magnet rotor 105; switching elements 107, 108; Hall element (not shown) for detecting the magnetic pole of the rotor; and control circuit 106. Control circuit 106 rotates the motor by turning on/off switching elements 107, 108 using a signal from the Hall element and, at the same time, controls the characteristics of the motor so as to be suitable for use.